Graham McTavish as Dwalin, left, Ken Stott as Balin, Martin Freeman as Bilbo, Richard Armitage as Thorin and William Kircher as Bifur in a scene from "The Hobbit: The Desolation of Smaug." (Warner Bros.)

And now, Sir Ian McKellen would like to make a clarification with regard to one of the most famous lines uttered by his wise wizard Gandalf in Peter Jackson’s “Lord of the Rings” films.

“You know, ‘You shall not pass’ isn’t in the book at all,” the legendary English actor pointed out, referring to the fantastic literature of J.R.R. Tolkien. “‘You cannot pass’ is what Tolkien wrote. We got it wrong.”

The man who Peter Jackson dubbed “the guardian of Tolkien” held forth on a wide range of subjects earlier this week at a special Hero Complex screening of the new fantasy “The Hobbit: The Desolation of Smaug,” the second installment in Jackson’s latest trilogy of films set in Middle-earth.

Arriving in theaters Friday, “The Hobbit: The Desolation of Smaug” sees Bilbo Baggins (Martin Freeman) continue on his journey to assist the company of dwarfs led by Thorin Oakenshield (Richard Armitage) reclaim their lands and the treasure now hoarded by the dragon Smaug (Benedict Cumberbatch).

Along the way they encounter a host of new friends and foes — including the valiant Tauriel (Evangeline Lilly), the first character wholly invented for one of Jackson’s Tolkien movies.

Presented in IMAX 3D at 48 frames per second, the Hero Complex screening took place Dec. 9 at New York’s AMC 34th Street 14 & IMAX, with McKellen on hand for a special Q&A following the film.

Watch the clip above to hear more of what the 74-year-old actor had to say about playing Gandalf this time out, and look for more clips from the conversation soon.

To find out first about upcoming films that will be featured in the Hero Complex Screening Series, follow us on Twitter: @LATherocomplex.

Azog existed. Died in the battle of the beginning of the movie. His son comes in the battle of the 5 armies to avenge his father (His son is Bold, or something like that). They keep him alive, but he existed in the Tolkien universe.

Azog is mentioned briefly in the novel The Hobbit by Gandalf, who says to Thorin, 'Your grandfather Thrór was killed, you remember, in the mines of Moria by Azog the Goblin,' to which Thorin responds 'Curse his name, yes'. Incidentally, this is the only place that Tolkien refers to Azog as a "goblin"; in other books such as The Lord of the Rings Tolkien describes him as a "great Orc."[2] This is not a discrepancy however, since as far as Tolkien was concerned goblin is merely the English translation of the word orc, not a different type of creature, and in The Hobbit he almost always referred to orcs as goblins.

Azog is largely mentioned in the Appendixes of LOTR, as many other characters and sequences of The Hobbit. Since Peter Jackson was not allowed to take parts of the Silmarillion, he turned to the Appendixes to enrich The Hobbit with further details.

I was fascinated not just by the visuals, but by how closely Jackson has kept to the feel of Tolkien. I could care less if he had invented a dozen characters, he's done it to make Tolkien's story work on the screen as well as possible, and I think Tauriel was a great addition.